This invention relates generally to lasers, and more specifically to a variable frequency dye type of laser that utilizes a short resonating cavity.
As is well known, a laser usually employs, as a central element, a pair of mirrors between which is positioned a light amplifying medium in solid, gas or liquid form. An optical cavity formed by the mirrors causes standing light waves to be generated between them and amplified by the laser medium. The frequencies of the standing waves depend, in part, upon the spacing between the mirrors, and thus the laser output frequencies are controlled by the mirror spacing.
Multiple frequency (multi-mode) oscillation is common, but more recently short cavity dye lasers have become commercialized. The resonant cavity mirrors are spaced apart only a few microns and result in a single oscillating mode because of such close spacing. The light amplifying medium in the cavity is a liquid dye. This type of laser is most appropriately used to emit short pulses of coherent light. The dye medium is excited to lase by application of a pulse of intense light from another, more conventional laser.
The frequency of the single mode output of such a dye laser can be adjusted by varying the space between the two mirrors. Manual adjustment of such spacing has previously been suggested, but this is difficult to achieve because of the very small mirror spacing variations that are involved. An improvement over the manual adjustment is a suggestion of an electrically driven piezoelectric transducer attached to one of the mirrors for moving it. Such a system is disclosed in U.S. Pat. No. 4,556,979-Scott et al. (1985). However, the laser dye cell structure suggested in that patent has been found to be difficult to implement in a practical dye laser device. Specifically, its piezeoelectric transducer provides a displacement of one mirror as a unit relative to the other, a characteristic that renders difficult and unreliable the initial adjustment of the very short distance between the mirrors as well as the replacement of dye material.
Accordingly, it is a primary object of the present invention to provide a tunable short cavity dye laser that is simple and compact in structure, reliable, easy to use, and which provides repeatable results.